Until now the output LCL-filters of grid coupled inverters are designed for low current ripple in the semiconductors. That means the main part of overall filter inductance is concentrated in the bridge side coil, whereas the grid side coil becomes comparatively small. This results in low controller robustness against grid impedance variations and in high inductor costs, since the core material of the bridge side coil is more expensive due to the high frequency requirements. The new approach should increase robustness and reduce costs without efficiency losings.
the answer of Mr. Mohamed Azab is so good that i feel i must to show my respect to him
This is a common problem. To improve the control performances there are many possible solutions can be formulated for the above type of problems.
1. Accurate filter parameter estimation. This problem is solved by advanced optimization techniques. By using these technique, the filter parameters can be computed and imroves the controller performance.
2.During the inverter design, if you use multi-level inverter, then the inverter is used to reduce harmonics or transients significantly. By which the burdern across the LcL filter is decreased. In this siruation, you can fix the inductor value eually to a lower value and used to protect system from any fault conditions.
3. By properly regulating the dc-link voltage of the inverter, the harmonics of the system and avialability of active power support is improved. In this condition also lower rating lcl filter is used for protecting the circuit. Due to lesser inductance, the controller performance of thebsystem imptoved.
For better understanding read my published papers and I guarenteed that you get idea from that
Thanking you
Buddhadeva Sahoo
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